BUG #15256: Comparing if a rowtype is null

The following bug has been logged on the website:

Bug reference: 15256
Logged by: Anderson Antunes
Email address: anderson(dot)ant(dot)oli(at)gmail(dot)com
PostgreSQL version: 9.3.5
Operating system: Windows
Description:

Hello. My name is Anderson Antunes. I'm from Brazil. I'd like to get more
information about the behavior of the query below using comparison
operators. From what I understand in the query result below, a composite
type variable is only null when all values are null. Similarly, a variable
is not null when all values are not null. However, when we have written a
null value and a non-null value, the "is_null" and "is not null" columns
remain false. I believe that if we have at least a pre-set value, the
operator should recognize that this variable is not null.
I hope you have understood what I think.

SELECT
r,
r IS NULL AS "is null",
r IS NOT NULL AS "is not null"
FROM (VALUES(NULL,NULL), (5, NULL), (5, 5)) r